1. Field of the Invention
The present invention relates to a high speed closing switch, and particularly, to a high speed closing switch in which a returning rod coupled to a movable electrode protrudes to an outer side of a case such that the returning rod may interwork with the movable electrode.
2. Background of the Invention
In general, a switchgear panel receives electric power and supplies electric power required for a load facility installed in each power customer, and to this end, the switch gear panel converts extra-high voltage power into a low voltage power and distributes the same to each customer. In general, the switchgear panel includes a switch, an arrester, a circuit breaker, an arc protection system, various measurement equipment, and the like.
The arc protection system includes a high speed closing switch. When the switchgear panel is normal, a high voltage electrode and a ground electrode of the high speed closing switch are maintained in an open state (non-conducting state), and when an arc accident occurs in the switchgear panel, the movable electrode positioned adjacent to the ground electrode is moved toward the high voltage electrode at a high speed such that the high voltage electrode is grounded through the movable electrode, thus bypassing a fault current.
In order to maintain an internally insulating state, the high speed closing switch is filled with an inert insulating gas, SF6, having excellent insulating characteristics.
As known, the high speed closing switch includes a high voltage electrode, a ground electrode, a movable electrode having a flange portion, first and second Thomson coils for moving the movable electrode to opening and closed positions of the movable electrode via the flange portion, and sensors for sensing the opening and closed positions of the movable electrode within a case formed of an insulating material such as an epoxy, or the like.
The high voltage electrode is connected to a bus of the switchgear panel and high voltage power is constantly applied thereto, and the ground electrode is grounded through a separate ground bus bar or a ground cable.
A first embodiment of the high speed closing switch is disclosed in Korean Patent Laid-Open Publication No. 10-2010-0063556A.
In the document of KR 10-2010-0063556A according to the first embodiment, a movable electrode of a high speed closing switch is positioned on a ground electrode side and open in a standby state, and when a fault current such as an arc occurs, a current is applied to a first Thomson coil disposed toward one side of a flange portion.
When the first Thomson coil is magnetized as the current applied thereto, an eddy current is generated at the flange portion of the movable electrode disposed toward one side of the first Thomson coil, and repulsive force is generated between electromagnetic force generated by the eddy current and electromagnetic force of the first Thomson coil.
Accordingly, the movable electrode is moved toward the high voltage electrode, and the high voltage electrode and the ground electrode are electrically connected through the movable electrode, whereby the high speed closing switch is in a closed state in which the fault current is grounded.
Thereafter, in case the movable electrode is to be returned to an open state, a current is applied to the second Thomson coil disposed toward the other side of the flange portion.
When the second Thomson coil is magnetized upon receiving the current, the movable electrode is moved toward the ground electrode according to an action of electromagnetic force based on the same principle as that described above, and the movable electrode is positioned in the original position, that is, positioned on the ground electrode side, whereby the high speed closing switch is in the open state.
As explained above, the high speed closing switch is placed in the open state or the closed state according to position of the movable electrode.
However, if movement of the movable electrode is defective and thus, the movable electrode fails to sufficiently move toward the ground electrode in the open state, a sufficient insulating distance is not secured between the movable electrode and the high voltage electrode, and thus, the movable electrode and the high voltage electrode are damaged due to defective insulation.
In addition, when the movable electrode fails to sufficiently move toward the high voltage electrode in the closed state due to defective movement thereof, a sufficient electrical contact is not secured between the movable electrode and the high voltage electrode and the movable electrode and the high voltage electrode are damaged by heating due to contact resistance therebetween.
For these reasons, in the high speed closing switch according to the first embodiment, contact sensors are installed within the case to recognize whether a position of the movable electrode is normal. When it is recognized that the movable electrode is in an abnormal position, rather than in an open position or closed position, the arc protection system informs a worker that the movable electrode is in the abnormal position.
However, in the high speed closing switch, the worker cannot recognize a position state of the movable electrode by intuition with his naked eyes, and since the contact sensors are installed within the case, reliability in recognizing the position of the movable electrode is degraded in case an electric line or a related circuit connected to the sensors are disconnected.
A second embodiment of the high speed closing switch according to the related art is similar to the configuration of KR 10-2010-0063556A of the first embodiment as described above. The second embodiment of the high speed closing switch according to the related art discloses that the second Thomson coil is omitted, and that in order to return a movable electrode to an open state, a flange portion of the movable electrode in a closed state is held by using a pair of returning rods actuated through external power and the movable electrode is returned to its original position, that is, toward the ground electrode.
In the high speed closing switch according to the second embodiment, when the movable electrode is returned to its original position, the returning rods are positioned in an initial standby state. This is because, when the flange portion of the movable electrode is repulsed by the first Thomson coil and moves again toward the high voltage electrode, the flange portion of the movable electrode is not to interfere with the returning rods.
In the high speed closing switch according to the related art second embodiment having the foregoing configuration, the movable electrode is opened, that is, returned, by the separate returning rods, while the movable electrode is closed by the first Thomson coil, and thus, the returning rods are considered not to mechanically interwork with a movement of the movable electrode.
As such, since the returning rods and the movable electrode do not interwork with each other, the worker cannot recognize a position of the movable electrode through a position of the returning rods.
Thus, in the high speed closing switch according to the second embodiment, although the returning rods protrude to outside of the case, since the returning rods do not interwork with the movable electrode, in order to recognize a position state of the movable electrode, contact sensors need to be installed within the case as in the high speed closing switch according to the technique of KR 10-2010-0063556A of the first embodiment described above. Thus, the high speed closing switch according to the second embodiment has the same problem as that of the high speed closing switch according to the first embodiment.
In addition, in the high speed closing switches according to the first and second embodiments, a fault current such as an arc is applied and components thereof are moved at a high speed, applying a big load. Thus, in the high speed closing switches according to the first and second embodiments, in order to secure operation reliability, the number of closing operations is set by capacity and by model.
In order to recognize the number of closing operations of the high speed closing switch, the number of operations of the movable electrode needs to be counted.
In the high speed closing switches according to the first and second embodiments, in order to count the number of operations of the movable electrode, a separate counting-dedicated controller is required to receive signals generated form the sensors according to movement of the movable electrode and accumulate the signals to count the number of operations of the movable electrode.
However, counting the operations of the movable electrode in an electrical manner degrades reliability, compared with a mechanical counter, in case an electrical line or a related circuit of the sensors or the counting-dedicated controller is disconnected.